David Winer writes, in How to avoid sounding like an monkey, that we should prefer the term “social network” over “social graph” when talking about models of people and their relationships. All right, his stick has a bit of a point on it…

“Now if you showed that diagram to most educated people, they probably would call it a network, and before we talked about social graphs we called them social networks, and you know what — they’re exactly the same thing, and social network is a much less confusing term, so why don’t we just stick with it? (Answer: we should, imho.) So if you don’t want to sound like an idiot, call a social graph a social network and stand up for your right to understand technology, and make the techies actually do some useful stuff instead of making simple stuff sound complicated.” (link)

If you (or our software system) is extracting, representing, visualizing, analyzing and/or manipulating date about people and their relationships as abstract graph models or as graph data structures, it seems very reasonable to use the term ’social graph’.